Girths measurements are circumference measures, using a tape, taken at standard anatomical sites around the body. The idea behind the selection of the body sites where the measurements are taken is, together they show a map of your current average of level subcutaneous or, below-the-skin, fat. Fat is hi-octane, readily-available fuel and, as such, fat levels in someone embarking on any athletic endeavour can be reduced over time. Collecting regular skinfold and girth measurements, combined with scale data, creates a vastly clearer picture of one’s body composition changes over time in response to regular training than referring to a weigh scale alone. Over time in active people, skinfold measurements all over the body will become gradually and relatively smaller. Lean tissue, metabolically active tissue weights more than fat and water and consumes substrates like fat for fuel. More muscle means more calories burned. If one’s diet is controlled, fat is gradually lost, consumed as fuel by the fitter, stronger muscles you’ll gain from training.